Effects of dietary gallic acid on growth performance, diarrhea incidence, intestinal morphology, plasma antioxidant indices, and immune response in weaned piglets

This study was conducted to evaluate the effects of dietary gallic acid (GA) at 100, 200, or 400 mg/kg on growth performance, diarrhea incidence, intestinal morphology, plasma antioxidant indices, and immune response in weaned piglets. A total of 96 male weaned piglets (25 +/- 1 days of age) with an initial body weight of 8.40 kg were allocated into 6 replicated pens (4 piglets per pen) for each of the 4 experimental treatments. On day 21, 24 piglets (1 piglet/pen) received an intraperitoneal lipopolysaccharide (LPS) injection. The blood samples were collected before (0 h) and 4 h after LPS challenge, and the piglets were slaughtered 4 h postchallenge to collect small intestinal samples. Dietary GA supplementation did not affect the growth performance of piglets (P > 0.05), but reduced diarrhea incidence was observed in piglets administered 400 mg/kg dietary GA compared with piglets fed a control diet (P < 0.01). In the jejunum, dietary GA at 100-400 mg/kg increased the ratio of villus height to crypt depth (P < 0.01), while dietary GA at 200 and 400 mg/kg reduced crypt depth (P < 0.01), and dietary GA at 100 mg/kg increased jejunum villus height (P < 0.01). In the ileum, dietary GA at 100 mg/kg increased the V:C ratio (P = 0.029). LPS injection reduced the activities of catalase, glutathione peroxidase and superoxide dismutase (P < 0.01) and increased the production of malondialdehyde (P = 0.054) and the contents of immunoglobulin (Ig) A, IgM, tumor necrosis factor (TNF)-alpha, and interleukin (IL)-8 (P < 0.01) in the plasma of piglets. However, there was no effect of diet on plasma antioxidant and immune indices (P > 0.05). Dietary GA linearly increased ileal secretory IgA content (P = 0.053). Moreover, dietary GA supplementation showed a linear effect on the expression TNF-alpha (P < 0.01); supplementation of 400 mg/kg GA significantly downregulated the expression of TNF-alpha in the ileal mucosa (P < 0.01). The trend analysis showed a linear effect of dietary GA supplementation on the ileal expression of IL-6 (P = 0.063), NF-kappa B1 (P = 0.045), and RelA (P = 0.062). In conclusion, dietary supplementation with GA in the basal diet contained 3000 mg ZnO/kg attenuated postweaning diarrhea and protected intestinal integrity, which may be attributed to the modulation of the intestinal local immune response by GA. Our results have implications for developing new strategies to enhance gut health and to decrease diarrhea in weaned piglets.